GKites: Wind Origins
3) Polar Easterlies. Trade Winds Intertropical convergence zone. Follows 30* latitude; where TRADE WINDS meet the prevailing WESTERLIES. Cold Front. The polar easterlies (also Polar Hadley cells) are the dry, cold prevailing winds that blow from the high-pressure areas of the polar highs at the North and South Poles towards low-pressure areas within the Westerlies at high latitudes. from the polar easterlies are one of the five primary wind zones, known as wind belts, . subpolar low or polar front subpolar high polar tradewind equatorial low.
Differences of temperature cause differences in pressure.
A zone where polar easterlies and westerlies meet is known as a(n) ____.? | Yahoo Answers
A difference in pressure across distances is called a pressure gradient, and this drives the wind. Here are two examples of air flow caused by pressure gradient. When a can of coffee is "vacuum packed," air is removed from the can. When the canis opened you can hear air rush in from the outside higher pressure.
Similarly, when you blow up a balloon you create a high pressure area because you compress the air and increase its density within the balloon.
When the balloon is punctured the air rushes outward to the lower pressure. In both examples air moves from higher to lower pressure, and the greater the difference the faster the air travels. Global Winds Once the air has begun to move surplus heat to the poles and surplus cold to the equator another force comes into play. This is called the Coriolis force, and is caused by the rotation of the earth.
Imagine yourself in a fixed position in space, looking down at the earth. You would observe that the wind moving from the equator to the north pole was traveling in a straight line, with the earth's rotating surface moving beneath it.
Now place yourself at a location on the earth's surface and observe the wind again. The wind would appear to be curving to the right. The earth rotates on its axis at the rate of miles per hour at the equator.
The speed decreases with increasing latitude until it is virtually zero at the poles. This is because the latitude circles grow smaller.
Place an object on the equator and allow 24 hours to go by. When the object returns, it will have traveled more than 24, miles - in other words, to travel that distance in 24 hours its linear speed was mph.
Now place the object at 60 degrees north and let it make its circle. In 24 hours it will travel about 12, miles at mph.
At the north pole the linear speed would be zero because there would be no distance traveled. As an object such as a piece of wind, or a rocket starts to move in a straight path from the equator to the north pole, its eastward speed the earth rotates from west to east will be mph. As it travels northward, its eastward movement will be faster than the eastward movement of the surface of the earth at higher latitudes.
It will run ahead of any object at higher latitudes, and appear to an earth based observer to be curving to the right.
Similarly, if the object traveled from the north pole to the equator it would have no eastward movement, and would fall behind a lower latitude object whose eastward movement would be faster. To an earth based observer the curve would again appear to be to the right of the direction of motion. Why is it, then, that in the southern hemisphere this apparent motion is reversed - that is, the Coriolis deflection is to the left?
Imagine yourself once again in space. This time you are hovering just above the north pole. When you look down at the rotation of the earth you see it moving counterclockwise. Now relocate yourself to just above the south pole. When you glance down, the earth is rotating clockwise. This explains why the apparent curve is to the right in the northern hemisphere and to the left in the southern.
In fact, as we continue to study wind motion, we'll see that each hemisphere is a mirror image of the other. Now one more imaginary placement of yourself. If you straddled the equator you would see neither clockwise or counterclockwise movement.
A zone where polar easterlies and westerlies meet is known as a(n) ____.?
Because of this, the Coriolis force is not in effect at the equator. General Wind Patterns Local wind patterns are the result of pressure differences in the immediate area: But there are global patterns that we can observe as well.
Let's start by following movement in the northern hemisphere. Hot air rises from the equator, creates a low pressure area, and flows towards the north pole. The upper wind flow is deflected to the right by the Coriolis effect, which causes it to pile up and move from west to east. The piled up air cools, creating a high pressure area, and sinks; and as it accumulates on the surface it flows towards both the equator and north pole.
The air moving toward the equator is influenced by the Coriolis effect and moves from the northeast, and because of its direction is called the northeast trade winds. Wind is classified according to the direction from which it is blowing.
In the old days when sailing ships were becalmed in this region, the ships often ran out of food and fresh water, causing any animals such as horses on board to die. These latitude bands became known as the horse latitudes. The descending air is very dry, so these latitude bands are where deserts are favoured in both the Northern and Southern Hemisphere. As surface air blows back toward the equator, it is turned to the right in the N.
Hemisphere, and to the left in the S. Hemisphere, due to the Coriolis effect. The result are the trade winds winds with a component from the east over the ocean surface. The figure below shows the Hadley cells. Idealized global circulation for Northern Hemisphere winter. The bulls-eye symbol indicates where a jet stream is coming out of the page toward the reader, and the "X" with a circle around it represents imagined tail feathers of jet-stream wind flowing into the page.
Note that the tropopause is the boundary between the troposphere, where our weather events take place, and the stratosphere, where the air is mostly dry. The stratosphere acts like a lid or cap on the weather that we experience in the troposphere. Mid-latitude Cyclones At mid-latitudes, such as Canada, there is not a strong vertical circulation cell.
Instead, the winds create large, horizontally swirling low- and high-pressure systems that we see on weather maps see figure below. High-pressure regions, called anticyclones, are associated with fair weather, clear skies, but light winds not good for sailing. Low-pressure regions, called extratropical cyclones, are associated with fronts, bad weather, and strong winds not good for pleasure sailing. Often the best sailing at mid latitudes is in between the highs and lows, where the winds are moderate and weather is still OK.
The Coriolis effect causes winds rotating counterclockwise around lows in the N. Hemisphere, and clockwise around highs. These circulations are superimposed by a general west-to-east movement of all the air at mid-latitudes. Winds are named by where they come from. At mid-latitudes is a general west-to-east air flow known as the Westerlies. Mid-latitude cyclones Lows and anticyclones Highs are imbedded in a general westerly flow; hence, these weather systems usually move from west to east.
The westerlies are generally stronger in the Southern Hemisphere because they flow over water. The westerlies in both hemispheres are stronger in winter than in summer. Surface winds around the globe, as is useful for trans-oceanic sailing. L and H indicate low and high pressure.
The air movements here are much weaker compared to those in the Hadley cells.